5^12/5^6 Is the correct response. When equal numbers with different exponents are divided then the you must subtract the exponents.
Thus 12-6 = 6.
The perimeter of each is the sum of the lengths of its sides.
Triangle Perimeter = 16 + 4x-3 +3x = 7x+13
Square Perimeter = 2x +2x +2x +2x = 8x
If these are equal, you have

The length of a side of the square is 26 units.